But Mayor Ignazio Marino is seeking to transform the avenue to something calmer, where Gucci loafers and sensible sneakers would rule.

Mr. Marino’s plan to ban private traffic on the roadway, which bisects a vast archaeological site, from the central Piazza Venezia to the Colosseum, has prompted grousing and histrionic debate over a project that conservators say would solidify the world’s largest urban archaeological area.

This being Rome, the first high-impact initiative of his seven-week-old administration, which goes into effect on Saturday, has provoked its share of unfavorable comparisons with the overweening ambitions of emperors past. “The mayor’s job is not to pass into history, but to work for his citizens,” said Luciano Canfora, a professor of classics at the University of Bari. “We already had Nero, that’s more than enough.”

He predicted the plan would “torture” other Romans with “catastrophic” traffic jams.

To the mayor, though, the project is the cornerstone of a bigger vision that plays on Rome’s strengths and uniqueness to develop a strategy for the city based on environmental and cultural sustainability.

“I want to change what was a highly trafficked street into a walk into history,” Mr. Marino, 58, said in an interview at his offices on the Capitoline Hill, which overlooks the Roman Forum. “It’s part of a dream of giving back to Romans, Italians and people from around the world this incredible place where the history of the Western world developed.”

Of course, modern Romans, and especially the neighborhood’s residents, have more practical concerns. Most have to do with the anticipated spillover effect of closing a broad avenue used by as many as 1,600 motorists an hour during peak times of day, according to city statistics.

Residents’ associations and local shopkeepers fret about aggravating the traffic congestion that is already as quintessentially Roman as the city’s famed cupolas, making their lives even more “invivibile,” a common Italian expression used by those complaining about life in the capital.

“We will block the streets, set up barricades,” pledged Luciana Gasparini, the president of Via Merulana per L’Esquilino, a neighborhood group that is organizing a protest against the project. (But, in Roman fashion, it will take place in September, once people have returned from their August holidays.)

Franco Aldini, a tailor with a shop on Via Labicana, complained that his business had already dropped since street work began in preparation for the closing. Mr. Aldini said he was considering suing the city for damages if the situation dragged on. “The mayor can’t decide from one day to the next to lock down a neighborhood,” he said.

But it seems that the mayor can, and did, forging ahead with a project that was a centerpiece of his campaign. In this first phase, the tract of Via dei Fori Imperiali closest to the Colosseum will be off limits to private vehicles, but not to buses and taxis. A rather optimistic simulation is visible on the city’s transportation Web site.

The final goal is to make the Via dei Fori Imperiali a pedestrian area from one end to the other, and to finance the project with subsidies from the European Union.

“I think Rome needed a kind of shock,” said the mayor, a former transplant surgeon, using the analogy of a person receiving emergency treatment. “The city had been sleeping and needed to wake up. After the shock, you go on to live a long, productive life.”

Mr. Marino spent nearly 20 years of his career as a doctor in the United States before returning to Rome in 2006, when he plunged into politics and was elected to the Senate with the center-left Democratic Party. This year, he decided not to run again at a national level but instead turned his sights on Rome, the city he “loves most in the world,” he said. Mr. Marino easily beat Gianni Alemanno, the incumbent, center-right mayor, in June. (…)